The Basics; A Good Neanderthal Was Hard to Find

By JOHN NOBLE WILFORD

Published: February 26, 2006

Maybe they just didn't have time to get to know each other.

The question of what Neanderthals and Homo sapiens might have done on cold nights in their caves, if they happened to get together and the fire burned down to embers, has intrigued scientists since the 19th century, when the existence of Neanderthals was discovered.

A correction in the way prehistoric time is measured using radiocarbon dating, described last week in the journal Nature, doesn't answer the enduring question, but it might at least help explain why no DNA evidence of interbreeding has been found: the two species spent less time together than was previously believed.

The old radiocarbon calculation is now known to be off by as much as several thousand years, the new research shows. That means that modern Homo sapiens barged into Europe 46,000 years ago, 3,000 years earlier than once estimated. But the radiocarbon dating under the new calculation also shows that their takeover of the continent was more rapid, their coexistence with the native Neanderthals much briefer.

The revised dates reveal an overlap between the species not of 10,000 or more years, as previously thought, but of only 2,000 to 4,000 in many places, perhaps 6,000 in others. The shorter overlap suggests that modern humans held a decisive advantage over Neanderthals after their arrival from Africa. Was that advantage cognitive, technological or demographic? Their personal ornaments and cave art, now seen to have emerged much earlier, are strong evidence for an emergence of complex symbolic behavior among the modern newcomers, a marked advance in their intelligence.

That doesn't mean they didn't interbreed with the Neanderthals.

As Katerina Harvati of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, points out, even the shorter length of coexistence was a long time. But it would have decreased the time available for cultural or genetic exchange.

''Since these two species may have been able to interbreed, as many closely related mammal species can,'' Dr. Harvati said, ''a restricted coexistence interval may be easier to reconcile with the observed lack of Neanderthal genetic contribution to the modern human gene pool and with the paucity of convincing fossil evidence for hybridization.''

The caves, it would seem, still hold their secrets. JOHN NOBLE WILFORD